In the manufacture of rubber articles, crude or raw rubber is compounded with various ingredients among which are sulfur and accelerators of vulcanization. The primary function of an accelerator or accelerator system is to increase the rate of the vulcanization process while allowing sufficient time to mix the accelerators into the rubber at an elevated temperature before vulcanization commences. This delay before the initiation of vulcanization is commonly referred to as scorch time.
The properties of a final rubber vulcanizate that are of importance include tensile strength, set, hysteresis, aging properties, reversion resistance and others. Other factors relating to the vulcanization which are of importance are the rate of cure, the cure time, the scorch behavior, the extent of cure, and tear resistance. These physical properties can be altered either beneficially or detrimentally through the inclusion of chemicals or components that impact upon the rate and state of vulcanization. Increasing performance requirements for tire continues to require improvements in the performance of tire rubber compounds.